Frames or lean-tos in which a certain number of small plants can be held tight, cultivated and handled are known. To get a mutual separation of the root systems of each small plant, every root system of the plants is sideways surrounded with a wall, which hinders root graft. These walls constitute a container around the root system of every plant and these containers can be mutually joined together to a frame or be placed in a lean-to, so a suitable number of plants can be handled in one flow of work, either by hand or machine. Each container can be filled with a suitable, comminuted growing medium, for instance, sphagnum, sand, granulated stonecrop or mixtures of these materials. The container wall, which surrounds each root system of the plants, has a forming effect on the roots of the plants because their growth is forced to follow the walls and may be the bottom. This forming effect has an unwanted effect on the root system of the plants and is called root deformation. The root deformations grow with increasing growing time in a container of a certain size. Root deformations are especially known in the production of container plants for use in forestry. These plants have bad wind firmness, hampered root growth or even cause root strangulation.
According to the invention the plant growing frame is peculiar because each growing medium of the plants is held tight in a way so they are mutually separated by an air space. To reach the wanted effect one can use form stable blocks as growing medium, for instance, rock wool, foam plastic or another suitable porous material, so that a container wall which, as mentioned, will deform the root system, can be omitted.
The air space between each growing medium block will hinder mutual graft of each root system of the plants, because the root tips will stop growing when they meet with the air space, and growth is initiated by the new root tips in the inner part of the system. This prodes, air-pruning, will repeat itself continuously until the plant with the growing medium block will be transplanted on the permanent habitat. At the same time of the transplanting, near the exterior sides of the growing medium block, active root tips will immediately grow out in the surrounding earth.
A decisive condition of the air-pruning effectively will hinder root graft from one growing medium block to another is that the air spaces are made in a way so that air can move freely under the bottom of the plant frame and vertically up between the growing medium blocks on all sides and allow air to pass between the growing medium blocks.
If the plant growing frame, out of consideration for its horizontal joining hinders such a free air movement, the comparative moisture of the atmosphere between the growing medium blocks will be so high that root graft will take place between the growing medium blocks themselves. This will decisively reduce the vitality of the plants, when they are separated and transplanted, because the plants by separated will loose a lot of their root system, in particular the part which is grown out into the surrounding growing medium blocks.
The plant growing frames known from British patent specification No. 1,426,313 are identical with those plant growing frames known from American patent specification No. 3,038,281, which all are characterized in that in the bottom the plant growing frame absolutely stop the vertical air movement between the growing medium blocks, because these plant growing frames are closed in the bottom between the growing medium blocks. The systems have also been given up because of the widespread root graft between the growing medium blocks.
The plant growing frame known from American U.S. Pat. No. 3,971,160 is different from the present invention because it does not use air-pruning at all. The transparent bag, which surrounds the plant growing frames will result in a high comparative moisture of the atmosphere so air-pruning will not take place. That is why the plant growing frame, according to the patent specification is made with vertical walls in the bottom between the growing medium blocks, so these walls hinder root graft. This plant growing frame is also closed in the bottom between the growing medium blocks.
As it appears from the above mentioned, the plant growing frame is decisively different, according to the patent specification from the present plant growing frame, which according to the invention is made in a way so it with air-pruning alone, achieved with an absolutely free air movement between the growing medium blocks effectively hinders root graft between the growing medium blocks themselves.
Hereby one achieves that the transplanted plant with all its root system quickly establishes itself on the permanent habitat with a quite natural root form without root deformations.
Therefore, the application still is said to concern a patentable invention.
A typical use of the plant growing frame according to the invention will be for production of trees for transplanting in woods. The plant growing frame will for a typical two-year nursery period held tight the growing medium blocks so they in all stages from direct seeding, growing, sorting and clearing up for delivering in the woods, are mutually separated of the air space, which will secure the wanted air-pruning of the root systems. The plant growing frame out of consideration for an effective handling will be used to transport the plants out in the wood to the habitat, where the plant with the growing medium block will be removed from the plant growing frame and transplanted, and out of the growing medium blocks and out in to the earth.